Function metatensor::c_api::mts_labels_union

pub unsafe extern "C" fn mts_labels_union(
    first: mts_labels_t,
    second: mts_labels_t,
    result: *mut mts_labels_t,
    first_mapping: *mut i64,
    first_mapping_count: usize,
    second_mapping: *mut i64,
    second_mapping_count: usize
) -> mts_status_t